Diagnosis of Viral Upper Respiratory Infections (Colds and Influenza)

The doctor will ask about your symptoms and medical history. A cold or influenza can be diagnosed based on your symptoms. In some situations, tests, such as throat culture or blood count, may be ordered to characterize the severity of the condition and identify other related problems.

Identification of the specific virus causing your symptoms is not usually necessary because it usually does not make a difference in treatment. However, if influenza A virus is suspected, on the basis of the time of year and community public health reports, people who are at high-risk for infection may be treated specifically for that virus.

Diagnosis may include the following:

Monitoring a fever—Taking your temperature every 6-8 hours can help define the severity of your illness.

Urinalysis—This is a routine check for conditions such as diabetes that may make your acute case of cold or influenza worse.
This is not usually done for colds or flu unless there is another reason to suspect urinary infection, such as suggestive symptoms or a fever with few other symptoms.

Blood tests—This is another routine test to assess your general health and your ability to fight off the illness.
It is not done routinely in colds or flu, but only if necessary such as if a person is very sick.

Throat Culture—This is done if there are signs or symptoms of sore throat in order to rule out strep throat, a bacterial infection.

Chest X-ray—If your doctor suspects that your upper respiratory infection has spread to your lungs, an x-ray may be done to check for pneumonia.

Revision Information

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.

Common cold. Merck Manual Professional Version website. Available at: http://www.merckmanuals.com/professional/infectious-diseases/respiratory-viruses/common-cold. Updated April 2014. Accessed August 11, 2015.

Influenza. Merck Manual Professional Version website. Available at: http://www.merckmanuals.com/professional/infectious-diseases/respiratory-viruses/influenza. Updated April 2014. Accessed August 11, 2015.